toddk911

I once read a post in here about modifications that could be done to the barn door spring that had the effects of a MAF system. They mentioned adjusting the pre load on the spring, much like shimming I guess.

Anyone???

nine-44

I popped the black cover off of my 88 N/A and dropped some tension off, it reved alot quicker and had better accel. Be sure to mark the stock position and don't try to remove the bolt holding the spring, it WILL break. Also keep a close watch on the A/F ratio. Make sure you don't run it out of fuel at the top end if you're pushing more boost. It will effect the idle, I adjusted with the car running. Just turn the black dial inside. Good Luck

blu951

Will it work on the 951?

Matt Sheppard

It merely tricks the DME into thinking you have more/less airflow and looks up a different fuel/timing map. If you are hooked up to an accurate sniffing device and tuning to pass smog, OK. . . just make sure it goes back to datum. Extra hp from your AFM spring is questionable.

Danno

How about just giving your AFM flapper-door the swiss-cheese treatment then?

Matt- send me an email about your chips....

Ski

The loosening or tightening of the barn door has helped a few cars that were running very rich. The theory behind this is that with the spring being tighter, this slowed the arm on the resistor plate in the AFM, thus "tricking" the DME as to the position of the arm, slowing fuel delivery, with the relation to engine RPM and air needs.

I tried it without much success. That's why I've worked with Danno to get a great set of chips for my car. My A/F is now 12.3-12.6 all the way to 5800 on full boost!

toddk911

Ok. I figred I'd ask. I am aso running GURU chips and a/f is not an issue anymore. Guess I'll leave it alone.

John..

Barn door adjustments with no other mods is not a good thing to do. I suggest you check the sensors in the engine to make certain they are in proper working order before diving into the AFM.

Danno

The AFM's door-angle to voltage-output is a precisely tuned calibration. The DME and its algorithm is tuned to work with this certain airflow-to-voltage curve. By changing the spring, you're changing the curve. However, it won't be linear across the board. By loosening the spring, you may cause the door to swing open further for any given airflow, thus tricking your DME into thinking you've got more flow, thus it will inject more fuel. But more fuel does not mean more power, only if you're running lean will it help.

The other downside to loosening the spring will be that the door is fully open earlier. This maxed-out position will occur before redline. However, once the AFM is fully open, voltage output will be fixed and the computer will think air-flow is constant. It will inject a constant amount of fuel. Problem is, air-flow is still increasing. So you'll end up with a mixture that gets leaner and leaner as RPMs increase after the flapper door is maxed-out. This is a similar problem to MAF sensors that are out of range for the air-volumes you want to flow.

blitz951

I spoke to someone at Kelly Moss Racing about an MAF kit and the guy there said dont waste money you will only gain 10 hp for 1500$, just send me your AFM and I will modify it to work just as good as the MAF. The problems is that he wouldnt tell me what the modification was and I didnt do it but if Kelly Moss said it could be done there must be something to mess with on the AFM. As far as the price I think is was like 250$, this was a long time ago so I can be too sure on the price.

Matt Sheppard

Well, Kelly Moss Racing knows there stuff and I dont contend this, but the barn door is a big restriction on airflow as is the "J" pipe to some degree, but the flapper is more of the problem. He might be talking about a similar mod to the Kokeln strait-through intake, but it wil still never get you the flow of a MAF that has literally NO restriction.